Scrollable and centered modals in Bootsrap

Introduction

Modals help show important info on top of the page. Making them scrollable and centered keeps content easy to read and looks neat on any screen.

When you have a lot of content in a popup and want users to scroll inside it.

When you want the popup to appear in the middle of the screen for better focus.

When you want a clean, user-friendly popup that works well on small or large screens.

Syntax

Bootsrap

<div class="modal fade" tabindex="-1">
  <div class="modal-dialog modal-dialog-scrollable modal-dialog-centered">
    <div class="modal-content">
      <!-- modal header, body, footer here -->
    </div>
  </div>
</div>

modal-dialog-scrollable makes the modal body scrollable if content is long.

modal-dialog-centered centers the modal vertically on the screen.

Examples

This modal is centered but will not scroll if content is long.

Bootsrap

<div class="modal-dialog modal-dialog-centered">
  <!-- centered modal without scroll -->
</div>

This modal allows scrolling but stays at the top of the screen.

Bootsrap

<div class="modal-dialog modal-dialog-scrollable">
  <!-- scrollable modal but not centered -->
</div>

This modal is both scrollable and vertically centered for best user experience.

Bootsrap

<div class="modal-dialog modal-dialog-scrollable modal-dialog-centered">
  <!-- scrollable and centered modal -->
</div>

Sample Program

This example shows a button that opens a modal. The modal is centered vertically and scrollable if the content is too long. This keeps the popup neat and easy to read on any screen size.

Bootsrap

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Scrollable and Centered Modal Example</title>
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>

  <!-- Button to open modal -->
  <button type="button" class="btn btn-primary" data-bs-toggle="modal" data-bs-target="#exampleModal">
    Open Scrollable Centered Modal
  </button>

  <!-- Modal -->
  <div class="modal fade" id="exampleModal" tabindex="-1" aria-labelledby="exampleModalLabel" aria-hidden="true">
    <div class="modal-dialog modal-dialog-scrollable modal-dialog-centered">
      <div class="modal-content">
        <div class="modal-header">
          <h5 class="modal-title" id="exampleModalLabel">Scrollable Centered Modal</h5>
          <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close"></button>
        </div>
        <div class="modal-body">
          <p>This modal is centered vertically and allows scrolling inside if content is long.</p>
          <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</p>
          <p>Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
          <p>Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.</p>
          <p>Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p>
          <p>More content to make modal scrollable...</p>
          <p>More content to make modal scrollable...</p>
          <p>More content to make modal scrollable...</p>
          <p>More content to make modal scrollable...</p>
          <p>More content to make modal scrollable...</p>
        </div>
        <div class="modal-footer">
          <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Close</button>
          <button type="button" class="btn btn-primary">Save changes</button>
        </div>
      </div>
    </div>
  </div>

  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/js/bootstrap.bundle.min.js"></script>
</body>
</html>

Important Notes

Always include aria-labelledby and aria-hidden for accessibility.

Use Bootstrap's JavaScript bundle to enable modal functionality.

Scrollable modals help keep the page behind visible and usable.

Summary

Use modal-dialog-scrollable to make modal content scroll inside the popup.

Use modal-dialog-centered to center the modal vertically on the screen.

Combining both classes creates a neat, user-friendly popup for long content.

Practice

1. What does the Bootstrap class modal-dialog-scrollable do in a modal?

easy

A. Disables modal animations

B. Makes the modal content scrollable inside the popup

C. Changes the modal background color

D. Centers the modal vertically on the screen

Solution

1. Step 1: Understand the class purpose

   The class modal-dialog-scrollable is designed to allow the modal content area to scroll if the content is too long.

2. Step 2: Compare with other classes

   Unlike modal-dialog-centered which centers the modal, this class specifically controls scrolling inside the modal.

3. Final Answer:

   Makes the modal content scrollable inside the popup -> Option B

4. Quick Check:

   modal-dialog-scrollable = scrollable content [OK]

Hint: Scrollable modals use modal-dialog-scrollable class [OK]

Common Mistakes:

• Confusing scrollable with centered behavior
• Thinking it changes modal size
• Assuming it affects modal background

2. Which is the correct way to add both scrollable and vertically centered behavior to a Bootstrap modal dialog?

easy

A. <div class='modal-dialog modal-dialog-scrollable modal-dialog-centered'>

B. <div class='modal-dialog scrollable-centered'>

C. <div class='modal-dialog scrollable centered'>

D. <div class='modal-dialog scrollable centered-modal'>

Solution

1. Step 1: Identify correct Bootstrap classes

   Bootstrap uses modal-dialog-scrollable and modal-dialog-centered as separate classes to add scroll and vertical centering.

2. Step 2: Check syntax for multiple classes

   Multiple classes are added separated by spaces inside the class attribute, so both classes must be included exactly as documented.

3. Final Answer:

   <div class='modal-dialog modal-dialog-scrollable modal-dialog-centered'> -> Option A

4. Quick Check:

   Use both classes separated by space [OK]

Hint: Use both classes separated by spaces inside class attribute [OK]

Common Mistakes:

• Using incorrect class names like 'scrollable' or 'centered'
• Combining classes into one word
• Missing one of the required classes

3. Given this modal HTML snippet, what will be the visual effect?

<div class='modal-dialog modal-dialog-scrollable modal-dialog-centered'>
  <div class='modal-content'>
    <div class='modal-body'>
      <p>Very long content here...</p>
    </div>
  </div>
</div>

medium

A. Modal is centered but content does not scroll

B. Modal content scrolls but modal is aligned to top

C. Modal content scrolls inside and modal is vertically centered on screen

D. Modal neither scrolls nor centers vertically

Solution

1. Step 1: Analyze classes used

   The modal uses both modal-dialog-scrollable and modal-dialog-centered classes.

2. Step 2: Understand combined effect

   These classes together make the modal vertically centered and allow the modal body content to scroll if it is long.

3. Final Answer:

   Modal content scrolls inside and modal is vertically centered on screen -> Option C

4. Quick Check:

   Both scrollable and centered classes active = scroll + center [OK]

Hint: Both classes together scroll content and center modal [OK]

Common Mistakes:

• Assuming scroll disables centering
• Thinking content scrolls outside modal
• Confusing modal-body scrolling with page scrolling

4. You added modal-dialog-scrollable but the modal content is not scrolling. What is the likely mistake?

medium

A. You forgot to add modal-dialog-centered

B. You must add scrollable class instead

C. You need to add overflow-auto to modal-content

D. You placed modal-dialog-scrollable on the wrong element

Solution

1. Step 1: Check where the class is applied

   The modal-dialog-scrollable class must be on the modal-dialog element, not on modal-content or others.

2. Step 2: Understand Bootstrap structure

   If placed incorrectly, the scroll behavior won't activate because Bootstrap styles target the dialog container.

3. Final Answer:

   You placed modal-dialog-scrollable on the wrong element -> Option D

4. Quick Check:

   modal-dialog-scrollable must be on modal-dialog [OK]

Hint: Apply scrollable class only on modal-dialog div [OK]

Common Mistakes:

• Adding scrollable to modal-content instead
• Confusing scrollable with centered class
• Forgetting to add modal-dialog class

5. You want a modal that is vertically centered, scrollable, and also has a fixed header and footer that stay visible while the body scrolls. Which Bootstrap structure and classes should you use?

hard

A. Use modal-dialog modal-dialog-scrollable modal-dialog-centered with modal-header, modal-body, and modal-footer inside modal-content

B. Use modal-dialog modal-dialog-centered only and add custom CSS for scrolling

C. Use modal-dialog-scrollable on modal-content and add fixed position to header/footer

D. Use modal-dialog modal-dialog-scrollable but omit modal-header and modal-footer

Solution

1. Step 1: Identify required classes for scroll and center

   Use both modal-dialog-scrollable and modal-dialog-centered on the modal-dialog element.

2. Step 2: Structure modal content properly

   Inside modal-content, include modal-header and modal-footer which remain fixed, while modal-body scrolls.

3. Step 3: Confirm Bootstrap default behavior

   Bootstrap automatically keeps header and footer visible when using scrollable modals with this structure.

4. Final Answer:

   Use modal-dialog modal-dialog-scrollable modal-dialog-centered with modal-header, modal-body, and modal-footer inside modal-content -> Option A

5. Quick Check:

   Combine scrollable + centered + header/footer structure [OK]

Hint: Use both classes on modal-dialog and include header/footer inside modal-content [OK]

Common Mistakes:

• Adding scrollable to modal-content instead of modal-dialog
• Omitting modal-header or modal-footer
• Trying to fix header/footer with custom CSS unnecessarily